In recent years, touch sensor panels, touch screens, and the like have become available as input devices. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface, and a display device, such as an LCD panel or an OLED panel, that can be positioned partially or fully behind the touch sensor panel or integrated with the touch sensor panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device.
Touch screens can allow a user to perform various functions by touching (or nearly touching) the touch sensor panel using a finger, stylus or other object. More advanced touch screens are capable of detecting multiple touches simultaneously. In general, touch screens can recognize the position of the one or more touches on the touch sensor panel, and a computing system can then interpret the touches, either individually or as a single gesture in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event.
When human fingers or other touch objects with a relatively large contact surface are used for operating a touch screen, the touch object may block the area underneath it on the touch screen from the user's view. This can affect the precision of the touch input. For example, one of the gestures commonly recognizable by existing touch screen devices is a single-touch tracking gesture that follows the movement of a touch by a user's finger or other object on the touch sensor panel. In response to the tracking gesture, the touch screen of the device can, for example, display a line as if it is being drawn by the object touching the screen. However, because the object is typically opaque, the exact point of interaction (or touch area) between the object and the touch screen is not visible to the user as he moves the object on (or over) the touch screen. This can prevent the user from accurately perform the gesture at the intended location on the touch screen, thus affecting the operation being performed (e.g., the drawing of the line) in response to the tracking gesture.